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问题 单项选择题

（）现象出现时，应对轨缝进行调整。

A、25m钢轨地段每公里瞎缝超过10％

B、25m钢轨地段每公里轨缝大于构造轨缝数量超过10％

C、12.5m钢轨地段连续出现2个瞎缝

D、12.5m钢轨地段连续出现3个轨缝大于构造轨缝

答案

参考答案：D

选择题

如图所示，在杠杆的两端分别挂着质量和体积都相同的铝球和铁球，这时杠杆平衡，然后将两个球分别浸没在稀硫酸和硫酸铜溶液中片刻，下列说法中正确的是（　　）

A．铝球一定是空心的

B．左边烧杯中的溶液质量减少了

C．去掉两烧杯后杠杆仍平衡

D．右边铁球出现红色
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填空题

  • (A) 条件(1)充分，但条件(2)不充分．
  • (B) 条件(2)充分，但条件(1)不充分．
  • (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
  • (D) 条件(1)充分，条件(2)也充分．
  • (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．

David has three credit cards: a Passport card, an Everywhere Card, and an American Local card. He owes balances on all three cards. Does he owe the greatest balance on the Everywhere Card
(1) The sum of the balances on his Everywhere Card and American Local card is $1, 350, which is three times the balance on his Passport card.
(2) The balance on his Everywhere Card is

of the balance on his Passport card and

of the balance on his American Local card.
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